<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script crossorigin src="https://unpkg.com/react@17/umd/react.development.js"></script>
    <script crossorigin src="https://unpkg.com/react-dom@17/umd/react-dom.development.js"></script>
<!--    用于解析ES6-->
    <script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>
</head>
<!--ES6 -->
<body>
    <div id="app"></div>
    <script type="text/babel">
        ReactDOM.render(
            <h1>hello world!!!</h1>, // JSX语法
            document.getElementById('app')
        )

        ReactDOM.render(
            <h1>hello world!!!哈哈哈哈哈</h1>, // JSX语法
            document.getElementById('app') // 如果同一个div中渲染两个内容，只会展示后面哪一个
        )
    </script>
</body>
</html>